After Marc's talk in the video meeting, we organized the nano-BPM collaboration in following three items@in a sequential order.
For the stabilization between two systems, there must be three major schemes;
The final experimental phase is a demonstration of beam control at nano-meter level with combination with FEATHER or FONT system, that is the fast feedforward/feedback test in a bunch-train. In this phase, the multi-train extraction must be very important.
He finally showed a possible layout; the SLAC/LLNL system at QD7-QF6, the KEK system at QD8-QF7 and the FEATHER/FONT at QF6-QD8. The optical anchor may be set at polarized positron area.
"GM measurement at ATF-floor and the reference system", H.Yamaoka
(transparencies, 21 pages, pdf, 2.6MB , or power point file, 9.6MB, and 3 figures of integrated amplitudes are here(PDF,619KB).)
Collaborating with Sugahara-san and Masuzawa-san, we (Yamaoka, Nicolas and Tauchi) measured ground motions at ATF. Three sensors (NS, EW, UD) were set each at two (floor) points in vicinity of QD7-QF6 and QF6-QD8, at north side of the extraction line. The sensor is an accelerometer (MG-102 of Tokyo-kiki) with resolution of 10-6 G ( about 1 mgal) . Sampling frequency was 256Hz and sensitive frequency region is greater than 1 Hz. Conditions are listed below;
Daily variation from 30nm(night) to 80nm(day) was observed in the integrated spectra of f >1Hz (8/26-27,8/29-30) while the 5 and 10Hz integrated ones have negligibly small variation. In Sunday, the daily variation became very small and the 1Hz integrated amplitudes were around 30nm. On Monday morning at 7am, 9/1, large ground motions were observed around 1 Hz, which were about 3 times larger than usual ones. They have very good coherency (~1) in all directions. On 8/28, two of three water lines were stopped for maintenance from 13:30 to 15:30. However, no apparent effect was observed in power spectra except for the last 10 minutes (15:20-15:30).
He demonstrated ground motions of the ATF floor by animation. He also updated the spectrum analysis of the reference frame(system) with a ground motion model based on the spectrum at 0:00pm, 1st September. Without using isolators, the 1st resonant peaks appear at 80~90Hz and ~270Hz in X,Z and Y directions, respectively. The peak amplitudes were less than a nano-meter, while typical amplitude(RMS) was about 5 nm at f=1Hz.
"Prototype designs", Y.Honda
Honda explained the design of (X,X') prototype mover. The X' has an inner plate of 6cm thick, which is supported with 8 hinges by outer frame. These hinges can support the plate with 500N (~50kg-G) force. Since the "rotational" center of the plate is not fixed, he devised a hinge structure (e.g. 2.6mm thick and 10mm long with necks at both ends) for enough rigidness so that the center movement can be limited within 1mm. Necessary rotation of 400urad can be achieved by 40um distortion of hinges. Major R&D item would be stability of the rotational center for such distortion.
The X and Y movers use 4 simple hinges of 0.3mm thickness and 10mm length, which can accept a distortion of 250um.
He tested Piezo devices with stacked structure, whose dynamic ranges are 80um/140V and 20um/27V in catalog. Resultant values were 17um/30V and 85um/50V with no-load.
He will complete designs of the prototype within this week (until 9/20). The prototypes will be manufactured at the KEK mechanical engineering center.